"Volumes are dead quiet today," said Douglas DePietro, head of equity trading at Evercore Partners. "Everyone is waiting for the big news later in the week."

The Federal Reserve is expected to announce Tuesday that it will leave key interest rates unchanged at very low levels -- but investors will be looking for clues as to how the central bank plans to proceed in the coming months.

Investors are also anxiously awaiting the Fed's report on how U.S. banks fared during the latest round of stress tests, which is due out Thursday. "The market could see a negative reaction if all the banks pass stress tests, but the Fed won't let them deploy much capital," DePietro said.

U.S. stocks finished higher for a third straight day Friday, after the government's monthly jobs report modestly exceeded expectations.

Also on Friday, Greece struck a deal with its private-sector creditors that will pave the way for the nation to secure new bailout funds and stave off a disorderly default.

Greece's deal triggered credit default swaps -- derivatives contracts that investors use to insure against default. But the Greek CDS market is very small and not expected to be disruptive to financial markets.

Economy: The February Treasury Budget report showed a higher-than-expected of $231.7 billion. Analysts had forecast a $229 billion, up from $222.5 billion in February 2011.

The national average price for a gallon of gasoline rose above the $3.80 mark Monday, resuming the advance that has plagued drivers throughout the winter.

The average price rose nine-tenths of a cent, according to the survey of gas stations conducted for the motorist group AAA. It was the third straight advance, with prices gaining 3.4 cents a gallon over Saturday and Sunday.